It has been noted that when inorganic fillers are combined with polyolefin resins, in order to decrease the heat of combustion of said resins and to provide compositions similar to wood or paper in appearance, that most inorganic filler particles have hydrophilic surfaces and consequently have a low affinity for the hydrophobic olefins. As a consequence, it has been difficult to incorporate sufficiently high contents of fillers into such polyolefins. Among the difficulties encountered have been the poor bonding of the filler particles to the polyolefin and the difficulty of properly incorporating the filler into the polyolefin by kneading operations. It has been found that the commonly used fillers of the prior art required considerable periods of time to ensure adequate and uniform distribution of the filler within the polymer matrix.
It has been difficult to completely and uniformly disperse the fillers in the matrix of the polyolefin resin by conventional kneading processes.
In order to overcome the above disadvantages it has previously been proposed to add a surfactant either to the inorganic filler material or to the polyolefin resin matrix. The surfactant was usually mixed into the matrix and not restricted to the interface between the filler and the matrix. As a result of the lack of segregation of the surfactant, inordinately high amounts of expensive surfactant were required and it has been noted that the melt-fall of the resultant composition during combustion is also increased. The melt fall is designed to describe the number of melted drops falling per minute when a sample of 2 millimeter thickness is burned according to ASTM D635. Lower rates are preferred.
When polypropylene is employed as the matrix for polyolefin type resins, the temperature of the resin at melting is in the vicinity of 200.degree. C. At this temperature vaporization of the commonly used surfactants occurs and consequently an objectionably strong odor is released due to the vaporization and decomposition of the surfactant. Also as a result of the vaporization, the surfactant, is removed from the melt composition and a decrease in the physical properties of the final composition results.